KR20120050497A - Metrology module for laser system - Google Patents

Abstract

The laser system 100 includes a laser 110, a housing 101 containing the laser, and a first chamber 120 arranged to receive laser beams from the laser during operation of the laser system. The system also separates the first chamber from the adjacent chamber, is disposed in the path of the laser beam 201, and the first optical element 220 forming a window between the first chamber 225 and the adjacent chamber. ; A beam splitter 210 disposed in a path of the light beam 201 upstream or downstream from the first optical element 220; And a ray detection device 240. During operation of the system, the beam splitter 210 receives the laser beam 201 and transmits the first portion of the laser beam as the main beam 201 to the beam detection apparatus and as the first sub beam. Directing the second portions 202, 203 of the laser beam.

Description

Measurement module for laser systems {METROLOGY MODULE FOR LASER SYSTEM}

This invention is an application accompanied by a priority claim on the basis of Provisional Patent Application No. 61 / 237,025, filed August 26, 2009, entitled "Shutter and Metrology Assembly," the entire contents of which are hereby incorporated by reference. Is incorporated in.

The present invention relates to a laser system, and more particularly to a measurement module for a laser system.

Electrically discharged gas lasers are known and have been put into practical use just after they were invented in the 1960s. The high voltage discharge between the two electrodes stimulates the laser gas, producing a gaseous gain medium. In a resonance cavity containing a gain medium, light is stimulated and amplified and then emitted from the cavity in the form of a laser beam. Most discharge gas lasers operate in pulse mode. A particular type of electrospun gas laser is an excimer laser. Embodiments of excimer lasers useful for lithography of integrated circuits are disclosed in US Pat. No. 7,567,607, issued on July 28, 2009 and entitled "High Repetition Rate Gas Discharge Laser Systems with Ultra-Narrow Band and Two Chambers". .

When used for integrated circuit lithography, excimer lasers are typically operated continuously in an integrated circuit fabrication line. It is very expensive to stop the line. For this reason, most of the components consist of modules that can be replaced quickly.

Embodiments of metrology modules used in laser systems are known. The modular instrumentation module facilitates installation and replacement operations in the laser system. Moreover, the module is relatively small so that it can be installed in a small space in the housing of the laser system.

In some embodiments, the metrology module specifically includes an optical assembly that can withstand harsh extended use in an industrial environment. For example, modules are used in high power ultraviolet laser systems, such as laser systems used in lithography tools. The module may include an optical element that is repeatedly exposed to high power ultraviolet laser beam but degrades relatively slowly.

In certain embodiments, the metrology module specifically includes optical elements that are bulk components without thin optical coatings (eg, uncoated wedge elements, uncoated parallel plate plates, or uncoated lenses). Under certain conditions, the bulk optical element can withstand longer exposure to high power laser beams than optical coatings that degrade in such environments. Thus, an uncoated optical element can be used to provide a more powerful metrology module.

In an embodiment, the module includes a beam pick off that derives one or more sub-beams from the main beam without causing significant degradation in the outgoing laser beam. The sub-beams, for example, have relatively low wavefront distortion, have a polarization similar to the main beam, and are easily separated from secondary reflection (eg, from the second surface) in the optics of the metrology module. As a result, a subbeam is made which is useful for various weighing measurements.

In some embodiments, the metrology module can efficiently measure information about the polarization state (eg, the ratio of orthogonal polarization states) of the main laser beam. Alternatively, or in addition, in certain embodiments, the metrology module may monitor the deformation in the direction of propagation (pointing) of the laser beam.

Various aspects of the invention (s) are summarized below.

In general, in one aspect, a characteristic laser system of the present invention comprises a laser; A housing comprising the laser and a first chamber (eg, purge volume) disposed to receive laser radiation from the laser during operation of the laser system; A first optical element that separates the first chamber from an adjacent chamber, is disposed in a path of a laser beam, and forms a window between the first chamber and the adjacent chamber; Beam splitters mounted in paths upstream and downstream from the first optical element; And a ray detection device. During operation of the laser system, the beam splitter receives a laser beam and transmits to the beam detection device a first portion of the laser beam as a main beam and a second portion of the laser beam as a first sub beam. Direct.

Embodiments of the laser include one or more of the following features and / or other aspects. For example, the light ray has a wavelength of less than 300 nm (wavelength of 248 nm or 193 nm). The laser is an excimer laser. The laser comprises an argon fluoride lasing gas medium.

The beam splitter and the ray detection device are disposed in the first chamber. A second portion of the laser beam, which forms the first sub beam, is reflected at the surface of the beam splitter.

The first optical element is a second beam splitter which, during operation, directs a third portion of the laser beam as the second sub beam along a path different from the path of the main beam. The laser system includes a second light detection device different from the first light detection device, and the second light detection device is positioned to receive a second sub beam.

The optical element is a wedge-shaped element. The optical element compensates for the deflection or offset of the main beam due to the beam splitter such that the path of the main beam after interaction with the optical element is parallel to the path of the light beam incident on the beam splitter.

The beam splitter directs the third portion of the light beam as a second sub beam in a direction different from the direction of the first sub beam. The beam splitter includes a first surface and a second surface that is not parallel to the first surface, wherein the first surface derives a first sub beam from the light beam, and the second surface is second from the light beam. Derive the sub-beam.

The beam splitter is a wedge-shaped member. In some embodiments, both the beam splitter and the optical element are wedge shaped members. All of the wedge-shaped members have a first optical surface, and the first optical surface of the beam splitter is parallel to the first optical surface of the optical element. The laser beam is incident on the first surface of the beam splitter, and the main beam of laser beam is emitted through the first optical surface of the optical element.

Both the beam splitter and the optical element each have a second optical surface facing each other and parallel to each other. The wedge-shaped members all have the same wedge angle. A portion of the wedge shaped member on the path of the laser beam consists of an uncoated surface (eg, the surface is free of optical coating such as antireflective coating). Either or both of the beam splitter and the first optical element comprise an uncoated surface.

The first optical element is arranged such that a light beam is incident on Brewster's angle on at least one surface of the first optical element.

The chamber is sealed from the adjacent chamber.

In general terms, in a further aspect, the characteristic assembly of the invention consists of a first wall and a second wall opposite the first wall, the first wall comprising a first aperture and the second wall being A chamber including a second aperture; A first beam splitter disposed in the chamber in a path between the first and second apertures; An optical element positioned at the second aperture; And a ray detection device. The beam splitter enters the chamber along a path through which the received light beam passes the first aperture, a portion of the light beam being directed to the additional optical element as a main beam, and a second portion of the laser light beam as the first sub beam. This is positioned to direct to the ray detection device.

Embodiments of the assembly include one or more of the following features and / or other aspects of the features.

In general, in another aspect, an apparatus for measuring information about polarization of a laser beam, which is characteristic of the present invention, comprises: a chamber; Disposed in the chamber to receive a beam of light from the laser during operation to direct a portion of the beam as a main beam along the first beam path and to direct a second portion of the beam to the first sub-beam along the second beam path. And a first beam splitter. The apparatus comprises: a ray detection device; A second beam splitter arranged to receive the first sub beam, to derive a second sub beam from the first sub beam, and direct the second sub beam to the light beam detecting apparatus; And an optical device disposed in a path of a first sub beam between the first beam splitter and the second beam splitter, the optical device being configured to change a polarization state of the first sub beam splitter.

Embodiments of the device include one or more of the following features and / or other aspects of the features. For example, the first beam splitter and the second beam splitter each have a reflecting surface, and in operation, the reflecting surface of the first beam splitter reflects a second portion of the light beam along a second beam path, The reflective surface of the two-beam splitter reflects a portion of the light rays of the first sub-beam to form a second sub-beam, wherein the reflective surfaces and the optics are orthogonal polarized light, wherein the second sub-beam is substantially the same as the main beam. It is arranged to have this mixed visible light.

The first beam splitter and the second beam splitter are arranged such that the second beam splitter has a radiation with mixed orthogonal polarization substantially the same as the main beam.

The first beam splitter and the second beam splitter are arranged such that the second beam splitter has light rays with transmittance in two orthogonal linear polarization directions, which are equivalent to the main beam.

The ray detection device has no diattenuation.

Each of the first beam splitter and the second beam splitter has a reflecting surface, and during operation, the reflecting surface of the first beam splitter reflects a second portion of the beam along the second beam path, and the second beam The reflecting surface of the splitter reflects a portion of the light rays of the first sub beam to form a second sub beam, and the reflecting surface is the second sub beam when there is no optical device in the path of the second sub beam. Orthogonal polarization, substantially the same as the main beam, is arranged to have mixed light rays.

The optical device is a polarization rotator. The polarization rotator rotates by 90 ° to form a polarization state of the first sub beam.

The optical device includes an optical element formed of a birefringent material. The optical device is a retarder (eg, half-wave plate).

In some embodiments, the optical device includes an optical element formed of an optically-active material. The optical device is a wedge-shaped member. The optically active material is crystalline quartz.

The ray detection device detects power or energy of the second sub-beam.

The apparatus includes a third beam splitter and a second beam splitter, wherein the third beam splitter is located in the path of the first sub-beam or in the path of the sub-beam transmitted from the second beam splitter and in operation A third beam splitter derives a third sub beam from the first sub beam or the transmitted sub beam and directs the third sub beam to the second light beam detection device. The third beam splitter is disposed in the path of the first sub beam between the first beam splitter and the second beam splitter. A third beam splitter is disposed in the path of the first sub beam between the first beam splitter and the optics. The first beam splitter, the second beam splitter, the third beam splitter, and the optical device are configured such that the main beam is relative to a coordinate system in which the second sub beam and the third sub beam are defined in a path of respective sub beams. And are arranged to have substantially the same polarization state. The first beam splitter, the second beam splitter, the third beam splitter, and the optical device are configured such that the polarization state of the third sub beam is determined by the coordinate system of the second sub beam with respect to a coordinate system defined in the path of each sub beam. It is arranged to rotate substantially 90 ° from the polarization state. The first beam splitter, the second beam splitter, and the third beam splitter may include the main beam and the second sub beam and the third sub beam in a state where there is no optical device in a path of the first sub beam. It is arranged to have substantially the same polarization state. The second beam splitter, the second beam splitter, the third beam splitter, and the optical device may be configured such that the polarization state of the third sub beam is in a state in which there is no optical device in a path of the first sub beam. It is arranged to rotate substantially 90 ° from the polarization state of the sub-beam.

In general, in a further aspect, an apparatus for measuring information about polarization of a laser beam, which is characteristic of the present invention, includes: a first beam splitter; A second beam splitter; And a ray detection device. In operation, the first beam splitter receives a beam of light from the laser, sending a portion of the beam as a main beam along the first beam path, and sending a second portion of the beam as a first sub-beam along the second beam path; The second beam splitter is arranged to receive the first sub beam, derives the second sub beam from the first sub beam, and sends the second sub beam to the ray detection apparatus; And the first beam splitter and the second beam splitter are set such that the plane of incidence of the laser beam with respect to the first beam splitter is not parallel to the plane of incidence of the laser beam with respect to the second beam splitter.

Embodiments of the device include one or more of the following features and / or other aspects of the features. For example, the apparatus includes an optical device disposed in the path of the first sub-beam between the first beam splitter and the second beam splitter and set to change the polarization state of the first sub-beam.

In some embodiments, the device comprises a third beam splitter and a second beam splitter, wherein the third beam splitter is located in the path of the transmission beam of the second beam splitter and, during operation, the third beam splitter is Derive a third sub-beam from the transmitted beam to the second light beam detection device, and wherein the third beam splitter has a plane of incidence of the laser beam with respect to the third beam splitter, the incident of the laser beam with respect to the first beam splitter It is set to be parallel to the plane. The third sub-beam has light rays of substantially different mixing in the orthogonal polarization state as the second sub-beam. An optical device configured to change the polarization state of the third sub-beam. The third sub beam and the second sub beam are used to correct the first light beam detecting device and the second light beam detecting device.

In general, in another aspect, a method of monitoring information about a polarization state of a laser beam, which is characteristic of the present invention, includes: separating a Jay beam from a laser into a main beam and a sub beam; Making a first measurement of the output or energy of the sub-beam; Performing a second measurement comprising measuring a polarization state of the sub as a measurement of the output or energy of the sub beam; And determining information about the polarization of the laser beam based on the first and second measurements, wherein determining the information comprises a ratio between each output or energy in the first and second measurements, or Calculating the difference.

Embodiments of the method include one or more of the following features and / or other aspects of the features. For example, changing the polarization state of the sub-beam includes rotating the polarization state of the sub-beam by 90 °.

In general, in another aspect, a method of monitoring information about a polarization state of a laser beam, which is characteristic of the present invention, includes: deriving a first subbeam and a second subbeam from a laser beam; Making a first measurement of the output or energy of the first sub-beam, using a first light detection device; Performing a second measurement on the output or energy of the second sub-beam, using a second light detection device different from the first light detection device; And determining information about the polarization state of the laser beam based on the first measurement and the second measurement, wherein determining the information about the polarization state comprises the respective measurements in the first measurement and the second measurement. Calculating a ratio or difference between the outputs or energies.

Embodiments of the method include one or more of the following features and / or other aspects of the features. For example, the first measurement and the second measurement are simultaneously executed. The polarization state of the second sub-beam is substantially rotated by 90 ° from the polarization state of the first sub-beam.

In general, in another aspect, a method of monitoring information about a polarization state of a laser beam, which is characteristic of the present invention, includes: deriving a first subbeam and a second subbeam from a laser beam; Performing a first measurement on the output or energy of the first sub-beam and the second sub-beam, using a first light detector and a second light detector; Performing a second measurement on the output or energy of the first sub-beam and the second sub-beam using each of the first light-detection device and the second light-detection device, wherein the first measurement and the second measurement Rotating at one of the polarization states of the first sub-beam; Determining a calibration factor based on the first measurement, comprising calculating a ratio or difference between the first measurement of energy of the first sub-beam and the first measurement of energy of the second sub-beam step,; And determining contents relating to the polarization state of the laser beam based on the second measurement and the calibration coefficients, wherein determining the information on the polarization state comprises determining each of the first and second subbeams. Calculating a ratio and a difference between each second measurement of energy.

Embodiments of the method include one or more of the following features and / or other aspects of the features. For example, each of the first measurements using the first sub beam and the second sub beam are performed simultaneously. Alternatively, or in addition, each of the second measurements using the first sub beam and the second sub beam are performed simultaneously.

The calibration coefficient is determined when the first and second sub beams have substantially the same polarization state as the main beam.

The polarization state of the second sub-beam is substantially rotated by 90 ° from the polarization state of the first sub-beam.

In general, in another aspect, an apparatus for monitoring a change in the propagation direction of a laser beam, characterized in that the invention comprises: a beam splitter arranged to derive a sub-beam from a laser beam; A sensor for monitoring a change in the position of the beam during operation; An optical element disposed in a path of a sub beam between the beam splitter and a sensor of a light beam and focusing the sub beam on the sensor; And a light conversion plate disposed between the optical element and the sensor. In operation, the light conversion plate absorbs light rays of the sub-beams of the first wavelength, emits light rays at a second wavelength different from the first wavelength, and the light rays of the second wavelength are detectable by the sensor.

Embodiments of the device include one or more of the following features and / or other aspects of the features. For example, the optical element is a lens or a mirror. The sensor is a position sensitive diode or quadrant photodiode. The sensor includes a detection surface having a maximum dimension, and the light conversion plate has a plate less than the maximum dimension of the detection surface.

The thickness of the plate is less than half of the maximum dimension of the detection surface (eg less than one quarter of the maximum dimension of the detection surface). The light conversion plate has a larger maximum dimension than the maximum dimension of the detection surface plus twice the thickness of the plate.

The apparatus includes a substrate supporting the light conversion plate, the substrate being positioned between the fluorescent plate and the sensor, at least some of the light rays incident on the fluorescent plate during operation, leading to the substrate, and the substrate The wave is guided to the edge of.

In another aspect, the characteristic system of the present invention comprises a laser and a device of the previous aspect, wherein during operation of the system the laser provides a laser beam from the beam splitter which derives the sub beam. The laser is an excimer laser. The laser beam has a wavelength of 248 nm or 193 nm.

The system includes an electronic processing device (eg, an electronic controller) in communication with the sensor, the electronic processing device being programmed to receive information from the sensor and output information about the change in the direction of the laser beam. do.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and are described below. Other features and advantages will be apparent from the description, drawings, and claims.

1 is a diagram illustrating various components of an embodiment of a laser system.
2 illustrates an embodiment of a laser beam pickoff assembly and a shutter assembly.
3 shows an embodiment of a laser beam pickoff assembly and a shutter assembly.
4 shows an embodiment of a configuration for energy measurement of neutral polarized light.
5 shows the configuration of the reflectances of p- and s-polarized light as a function of the angle of incidence.
6 shows an embodiment of a configuration for measuring energy of neutral polarization of light beams emitting a laser.
FIG. 7A shows an embodiment of a configuration for polarization measurement of light beams emitting lasers. FIG.
FIG. 7B is a flow chart for polarization measurement using the apparatus shown in FIG. 7A
8 shows a graph of relative signals at an energy detector as a function of polarization ratio.
9 shows an embodiment of a configuration for energy measurement and polarization measurement of simultaneous neutral polarization.
FIG. 10A illustrates a configuration for calibrating the settings shown in FIG. 9.
FIG. 1OB is a flow chart of a method of using the system of FIG. 10A.
FIG. 1OC is a flow chart for another method of using the system of FIG. 10A.
11 illustrates an embodiment of a beam pointing metrology assembly.
12 shows the configuration of the output beam intensity in the diode.
13 shows an embodiment of a metrology module having two submodules.
FIG. 14 shows an embodiment of the measurement module of FIG. 13.
15 shows an embodiment of a configuration for two-dimensional imaging of a laser beam.
16A shows an embodiment of a detector assembly.
16B shows another embodiment of a detector assembly.
17 shows an image measured by a CCD camera.
18 shows an embodiment of an assembly for speckle contrast measurement.
FIG. 19 illustrates a folding scheme for the metrology assembly of FIG. 18.
20 shows the layout of a camera for various measurements.
21 shows an embodiment of a rotary feedthrough using a shaft seal.
22 shows an embodiment of the manual drive unit.
Fig. 23A shows an embodiment of a pneumatically driven linear actuator.
FIG. 23B is an enlarged view of the pneumatically driven linear actuator of FIG. 23A. FIG.
24 shows an embodiment of a microlithography apparatus.

Like reference numerals in the various drawings indicate like elements.

Referring to FIG. 1, the laser system 100 includes a laser module 110, a measurement module 120, an electronic module 130, and a housing 101 surrounding a gas supply 140. The laser module 110 and the measurement module 120 are further enclosed in the purge volume 151, and the gas supply unit 140 is connected to the purge volume 151. The gas supply unit 140 and the purge unit 150 provide a controlled atmosphere in which the laser module and the measurement module can operate. The electronic module 120 communicates with the laser module 110 and the metrology module 120 to control the operation of the system. During operation of the laser system 100, the laser module 110 generates a laser beam that is directed to the metrology module 120. The metrology module 120 measures various attributes of the laser beam before the beam exits the system 100 as the output beam 160.

The laser module 110 includes an optical cavity, a gain medium, a pump (eg, an optical pump) and associated laser optics. In some embodiments, the laser module 110 is an excimer laser module.

The measurement module 120 includes various optical elements and one or more light detectors for characterizing the light beams received from the laser module 110. Various embodiments of optical assemblies that may be included in metrology module 120 are described below.

The electronic module 130 includes an electronic controller and a power supply unit. The output of the light detector is interfaced with the electronic module 130 which in turn controls the electrical signal sent to the laser module 110, affecting or modifying the operation of the laser cavity.

The gas supply unit 140 includes a gas treating apparatus and supplies a purging gas to the purge volume 151. In some embodiments, the purge volume corresponds to a portion of laser system 100 through which a laser beam propagates. The gas supply unit 140 supplies a gas suitable for propagation of light rays, for example, a gas inert to light rays, to the purge volume. In certain embodiments, the purge volume can be purged with nitrogen.

The purge volume 151 is shown in FIG. 1 as a single volume, and generally the structure of the purge volume can be changed. For example, purge volume 151 includes a plurality of chambers, each sealed for the others. In general, the purge volume 151 provides a controlled atmosphere in which the laser beam propagates before the laser beam exits the laser system 100.

Moreover, although the laser module 110 and metrology module 120 are generally shown as being entirely contained within the purge volume 151, any component of these modules may be housed outside of the purge volume. For example, in some embodiments, the detector of metrology module 120 lies outside of purge volume 151. This arrangement includes placing an input face of the detector in proximity to the purge volume. This arrangement has the advantage that only the input face of the detector is sealed in the purge volume. The outside of the detector is arranged outside the purge volume, thereby minimizing the use of electrical feedthrough in the purge volume. In alternative embodiments, instead of one signal purge volume for the laser module and metrology module, a plurality of purge volumes may be divided into individual volumes, each having a housing and a sealing portion.

In general, the wavelength of the output beam 160 may vary depending on the type of laser module used. In some embodiments, the laser system 100 emits light having a wavelength of less than 300 nm. For example, laser system 100 may be an excimer laser that generates output light rays having a wavelength of 248 nm or 193 nm. The laser module 110 may include a laser gas processing laser medium, such as molecular argon fluoride, which generates output light at 193 nm.

As noted above, in general a variety of different assemblies may be used in the metrology module 120. In some embodiments, the metrology module 120 includes a pick-off assembly to derive one of the plurality of sub beams from the laser light. An embodiment of the pickoff assembly is shown in FIG. 2. Here, the main beam pickoff assembly 200 includes a first beam splitter 210 and a second beam splitter 220. Pickoff assembly 200 also includes a shutter mirror 230 and a power sensor 240.

Both beam splitters 210 and 220 are wedge shaped members, and respective beam splitter surfaces in the path of the main beam 201 entering the metrology module pick up each sub beam. The sub beams are indicated by reference numerals 202, 203, 204 and 205 in FIG.

The main beam 201 exiting the laser module 110 is incident on the beam splitter 210 and part of the main beam is picked off as the sub beam 202 for measurement. One or more subbeams (eg, subbeams 202 and 203) are generated by the beam splitter 210. A portion of the main beam 201 is transmitted through the beam splitter 210 and then enters the beam splitter 220. One or more subbeams (eg, subbeams 204 and 205) may be generated by reflection from the beam splitter. A portion of main beam 201 is transmitted through beam splitter 220 and then directed to shutter mirror 230 that selectively inserts or removes from the beam path of main beam 201. When the shutter mirror 230 is removed from the beam path of the main beam 201, a portion of the main beam 201 transmitted through the beam splitter 220 enters the power sensor 240. Power sensor 240 may be of the type described in US Pat. No. 7,567,607, for example, the contents of which are incorporated herein throughout. Once the power sensor 240 is removed from the path of the main beam 201, the main beam 201 exits the metrology module 220 and is directed for use in further applications downstream of the laser system 100.

Due to the orientation of the surfaces of the beam splitter 210 with respect to the main beam 201 and the refraction occurring on the surfaces, the main beam 201 is spatially offset and once by the beam splitter 210 It is deflected with respect to the propagated initial propagation direction. The wedge-shaped second beam splitter (ie, reference numeral 220) can correct the beam offset and deflection of the main beam introduced by the wedge-shaped first beam splitter (ie, reference 210). In some embodiments, it is glass that the inlet surface 212 of the wedge shaped beam splitter 210 and the outlet surface 224 of the beam splitter 220 are parallel (or nearly parallel).

Alternatively, or in addition, the outlet surface 214 of the beam splitter 210 and the inlet surface 222 of the wedge-shaped beam splitter 220 may also be parallel (or nearly parallel). In such a configuration, beam deflection, color effects and beam enlargement or reduction due to symmetry are relatively small, even if present. The thickness of these wedge shaped beam splitters and the distance between them are selected to reduce the beam offset by the wedge shaped beam splitter. The beam offset is zero in some embodiments, or set to another desired value.

In some embodiments neither the beam splitter 210 nor the optically active surface of the beam splitter 220 includes an optical coating.

Wedge-shaped beam splitters may be advantageous over thin and substantially parallel plane-parallel beam splitters because they allow for relatively easy separation of the beams reflected from different surfaces of the beam splitter. This allows for easy separation of a single sub beam for metrology purposes. For example, the reflection of the incident beam from the first (inlet) surface and the second (outlet) surface of the thin parallel plated beam splitter may be too spaced apart and propagate along the parallel path, so that one sub This makes it difficult to separate the beam from other sub beams.

Using a wedge shaped beam splitter that does not use a coating surface is more advantageous than a beam splitter utilizing optical coating (eg, anti-reflective, to reduce unwanted second surface reflections from the beam splitter). AR) coating, the uncoated surface is naturally arranged to have a relatively low reflectivity (eg, within the range of about 1%), so that the optical coating when exposed to laser light (eg, exposure to continuous high power) Deterioration does not occur.

Although the beam splitters 210 and 220 have a wedge shape in the assembly 200, generally other direct beam splitters may be used. For example, parallel planar beam splitters (eg, with or without optical coating) may be used.

As mentioned above, the two wedge shaped beam splitters shown in FIG. 2 together provide four individually reflected sub-beams. In general, any number of these subbeams can be used for metrology. The beam splitter can be designed so that each beam has different properties. For example, different beams may include different relative power or polarization characteristics, depending on how the beam is used in the system. For example, in some embodiments, two sub beams are used for metrology and the other two can simply be discarded (eg, directed to the beam stop). Thus, the beam splitter can be configured such that the two discarded sub beams contain very little or no energy, depending on the degree of polarization of the laser.

In some embodiments, the surface of the beam splitter is arranged at Brewster's angle with respect to the incident beam. This arrangement can reduce (eg, minimize) the transmission loss at that surface. The Brewster's angle θ _B is calculated as θ _B = tan ⁻¹ (n _t / n _i ), where n _t is the refractive index of the transmission medium and n _i is the refractive index of the medium at the point where the incident beam is incident . At the Brewster's angle, all light rays with a polarization component (p-polarization) parallel to the plane of incidence are transmitted at the interface, reflecting only the incident light polarization component (s-polarization) perpendicular to the plane of incidence.

In some embodiments, both the inner surfaces 214, 224 of the wedge shaped beam splitter are arranged at the Brewster's angle with respect to beam incidence on that surface, thereby minimizing transmission loss in the main beam 201. For example, assuming that the laser beam shown in FIG. 2 is polarized primarily parallel to the paper plane, as a result of the Brewster's angle arrangement, the subbeams 203 and 204 have very little or no energy. do not include. However, in certain embodiments, the optical assembly can be arranged to produce each of four reflective beams that can be supplied to other light detectors or other instruments with sufficient energy.

For example, considering the case where the wedge-shaped beam splitter has a refractive index of 1.50 (i.e., a beam splitter made of calcium fluoride at a laser beam wavelength of 193 nm), the outer surface 212 has a main beam ( When the beam splitter has a wedge angle of 5.569 ° when oriented at an angle of 45 ° with respect to the beam path of 201 (which causes reflection at 90 ° with respect to the sub-beam 202 directed to the light detector), At the inner surface 214 of the beam splitter the state of the Brewster is obtained. The reflectances for two different orthogonal linear polarizations at each wedge surface are:

External surface 45 ° with respect to main beam 201 (e.g., 212 and 224): 0.85% (p) / 9.24% (s)

Internal surface at Brewster's angle (eg, 214, 222): 0.00% (p) / 14.86% (s)

Thus, for this configuration, the total transmission loss of the main beam due to the pickoff assembly 200 of the main beam is 1.7% p-polarized and 40.3% s-polarized. If the laser beam is almost completely p-polarized, the loss is less than 2%. Thus, due to the difference in transmittance between s-polarized light and p-polarized light, the pickoff assembly 200 of the main beam also helps to clean up the polarization of the main beam 201.

Alternatively, if a ray enters surfaces 212 and 224 at an angle different from 45 °, the wedge angle is adjusted to match the Brewster's angle at the inner surface.

In some embodiments, beam splitter 220 is integrated into housing partition 225, as shown in FIG. 2. Housing partition 225 is used to define the purge volume. In this embodiment, the beam splitter 210 is located in one purge volume defined on the left side of the housing partition 225, while the shutter mirror 230 defines another purge volume defined on the right side of the housing partition 225. It can be located at In some embodiments, the beam splitter 220 is used as the exit window of the metrology module 120 and in some cases as the exit window of the laser system 100.

In some embodiments, housing partition 225 includes an indium film in contact with beam splitter 220. Depending on the sealing scheme used for the housing partition 225, mechanical stress is applied to the beam splitter 220. When mechanical stress is applied to the beam splitter 220, the wavefront is induced into the sub beams 204 and 205. Thus, such sub-beams are not suitable for measurements (eg beam profile measurements) where low wavefront distortion is required. As a result, in some embodiments, the subbeams 204 and / or 205 are used for metrology measurements such as being insensitive to relatively wavefront deformation, such as, for example, spectrum or energy measurements.

On the other hand, the beam splitter 210 is installed in the assembly 200 in a manner that is relatively stress free compared to the beam splitter 220 because it is not integrated with the housing partition. Thus, in certain embodiments, subbeams 202 and / or 203 are used for wavefront sensitive measurements such as imaging.

In general, various attributes of the main beam 201 may be measured via the sub beams 202-205. For example, metrology module 120 may include one or more beam profiles, beam positions, beam divergence, beam pointing, wavefront, pulse duration, pulse energy, polarization characteristics, spectrum, bandwidth, wavelength, speckle of the main beam. It is used for measuring contrast, transverse or temporary coherence length.

When the beam splitter 210 is located upstream of the beam splitter 220, in the embodiment shown in FIG. 2, alternative arrangements are possible. For example, in some embodiments, beam splitter 210 is located downstream from beam splitter 220. That is, the beam 201 is incident on the beam splitter 220 before the beam splitter 210.

The shutter mirror 230 is connected to an actuator (eg, an electromechanical actuator) that controls the output of the beam 201 from the laser system 100 and optionally inserts the mirror into the path of the main beam 201. When the shutter mirror 230 is inserted in the path of the main beam 201, there is no light output (or negligibly small) exiting the laser system 100. Instead, the main beam is directed from the shutter mirror 230 to a beam dump (eg, a water cooled beam dump).

In some embodiments, the shutter mirror 230 is arranged to return the main beam through the beam splitter 220 and direct it to the beam dump at a suitable location immediately next to the main beam path. Such a configuration can help to alleviate space constraints. In a particular embodiment, the shutter mirror 230 can replace one of the beam splitters when the shutter mirror is inserted in the beam path of such main beam 201, so no additional space is needed by the shutter mirror 230.

In certain embodiments, the prism shutter can be used instead of a mirror. For example, referring to FIG. 3, the right angle prism 330 is used as a shutter. When the shutter prism 330 is not inserted into the beam path of the main beam 301, the beam splitters 310 and 320 generate the sub beams in the manner described above to direct the sub beams to one or more ray detectors. do. A shutter prism 330 is inserted into the beam path of the main beam 301 between the beam splitter 310 and the beam splitter 320 to prevent the main beam 301 from exiting the laser system 100. The main beam 301 enters the input face of the shutter prism 330, undergoes total internal reflection at the hypotenuse face of the prism, and is substantially perpendicular to the initial propagation path of the main beam 301. After coming out, head to the beam dump.

The optical surface of prism 330 may not be coated. Since the laser beam can cause a degradation of the coating, the uncoated surface can withstand greater exposure to the laser beam than the coating surface. For example, excimer lasers of less than 300 nm can degrade the multilayer coating used to form dielectric mirrors. Thus, uncoated prism shutters have a longer life compared to coated shutter mirrors. In addition, the arrangement shown in FIG. 3 also allows less space to be used to direct the main beam to the beam dump when the light beam should not exit the laser system 100.

As described above, the energy of the sub-beam picked off from the beam splitter 210 is always sensitive to the polarization state of the main beam 210 when the surface uncoated on the beam splitter 210 is used. In order to obtain energy measuring means that does not depend on the polarization state of the laser, the measurement assembly is arranged such that the polarization state of the light beam in the energy measurement apparatus substantially coincides with the polarization state of the main beam. If the polarization states of the two light beams coincide, the concentrations of the light beams measured in the two orthogonal polarization directions of the two beams are substantially the same. This concentration can be obtained by measuring the amount of light transmitted after a polarizer aligned in each of the two orthogonal polarization directions is placed in the beam. In addition, the polarization state of the light ray can be said to be a mixture of orthogonal polarizations included in the beam. For example, the ratio of s-polarized light and p-polarized light included in the beam relative to the incident surface of the surface where the beam was last reflected is the same in both beams when the two beams have the same polarization state. That is, the two beams have zero diattenuation, which is the differential attenuation (eigenpolarization) of the amplitude of the parallel polarized light and the amplitude of the vertically polarized light with respect to the two orthogonal polarization directions. The idea of polarization state matching can also be expressed in terms of Stocks parameters. When the polarization state of the sub beam is the same as the main beam, S ₁ / S ₂ and S ₂ / S _{0, which} are normalized Stokes vector components in both the sub beam and the main beam, are the same.

In some embodiments, the two orthogonal polarization directions are two orthogonal linear polarizations.

For accurate measurement of the energy of the main beam, a polarization-neutral pick-off scheme is used that generates a sub beam having the same polarization state as the main beam. For example, a beam splitting surface using two Fresnel reflections from an uncoated surface, each having incident surfaces oriented in a non-parallel manner with respect to each other, provides a pickoff of neutral polarization. can do. The plane of incidence of the surface is a plane including both the normal vector and the propagation vector of incident light on the surface.

Referring to FIG. 4, pickoff of neutral polarization is achieved by using beam splitter 410 where the main beam 401 is hit at an angle of incidence of 45 °. To illustrate how to obtain a pickoff of neutral polarization, for example, considering the case where the main beam 401 has the same polarization mixture (50% each) of p- and s-polarized light, p-polarized light And s-polarization is defined in relation to the plane of incidence of the light rays in the beam splitter 410. Due to the incident angle (45 °) of the main beam 401 in the beam splitter 410, the p-polarized R _p and the s-polarized R _s in the main beam 401 are referred to as the sub beam 402. Reflected at beam splitter 410, it is directed to beam splitter 420. R _p and R _s are the reflectances of p- and s-polarized light on the surface. Beam splitter 420 is oriented such that the plane of incidence is not parallel to the plane of incidence of beam splitter 410. Similarly, beam splitter 420 is oriented at 45 ° relative to subbeam 402. As a result of the beam splitter 420 being oriented, the p-polarized light R _p contained in the sub-beam 402 picked off from the main beam 401 is now s-polarized with respect to the plane of incidence of the beam splitter 420. This R- _s , which is the s-polarized light, is reflected by the beam splitter 420 as the sub beam 403 and directed to the energy measuring device 430.

After reflecting off the beam splitter 410 and the beam splitter 420, the total R of the p-polarized light contained in the main beam 401, defined for the beam splitter 410, is R _p. X R _s ) is directed to the energy measuring device 430. Likewise, the s-polarized light defined for beam splitter 410 becomes p-polarized for beam splitter 420 due to the orientation of beam splitter 420. Accordingly, the beam splitter 420 reflects R _p of this light beam and directs it to the energy measuring device 430. After being reflected by the beam splitter 410 and the beam splitter 420, the R ( R _s × R _p ) of the _s -polarization included in the main beam 401, defined for the beam splitter 410, is an energy metering device. 430, the ratio is the same as for p-polarized light.

As a result of the optical configuration shown in FIG. 4, the mixing of the light rays having the orthogonal polarization direction included in the subbeam 403 becomes the same as the mixing of the light rays having the orthogonal polarization direction included in the main beam 410. For example, when two beam splitters are oriented at 45 ° with respect to each incoming beam, R _p is 0.085%, R _s is 9.24%, and R is 0.0785%. In contrast, the sub-beam 402 generated by reflecting one from the beam splitter 410 has a ratio of s-polarized light to p-polarized light of 10.8 (9.24% / 0.85%).

As a further example, considering the case where main beam A and main beam B, both having the same energy, have different mixing of s-polarized light and p-polarized light,

Table 1 s-polarized light p-polarized light Energy ratio of main beam Main beam A 10% 90% 1.689% Main beam B 90% 10% 8.401%

The last column of Table 1 shows the energy ratio of the main beam included in the sub beam after being single reflected from the beam splitter. Therefore, two beams having the same energy but in different polarization states are measured with different energy in the beam energy measuring device 430 unless the energy measuring pickoff is performed by the neutral polarization method. This example shows the importance of the energy measurement of neutral polarization for the main beam.

The same 45 ° incidence angle in the beam splitter 410 and the beam splitter 420 is one of several configurations available for the setup shown in FIG. 4. For example, the setting may be configured with the same incident angle (other than 45 °), which is different from the above in the beam splitter 410 and the beam splitter 420. Alternatively, the setting may be configured at different incident angles in the beam splitters 410 and 420. For example, one beam splitter is arranged to have a surface that is an angle of incidence above the Brewster's angle, and the other is that the ratio (p / s ratio) of the reflectance of p-polarized light and s-polarized light is positive for both incident angles. During the same, it is as follows.

5 shows the reflectance of p / s as a function of the angle of incidence. In addition, several options for the angle of incidence are listed in Table 2. In general, the reflectance of p-polarized light can be calculated using the following equation:

And the reflectance of s-polarized light can be calculated by the following equation:

Where θ _t is the angle created between the normal surface and the transmitted beam in both equations.

Table 2 Angle 1 Angle 2 Transmission rate of main beam to energy measuring device 45 ° 45 ° 7.9 × 10 ^-4 30 ° 30 ° 1.47 × 10 ^-3 45 ° 67.4 ° 2.21 × 10 ^-3

The pair of angles of incidence differ from the two 45 ° reflections in the beam splitter 410 and the beam splitter 420 so that the energy of the subbeam 403 is higher than the energy obtained from the two 45 ° reflections. Or to a lower level. In this way, the energy of the subbeam 403 can be tailored within the measurement range of the energy measurement device 430.

The configuration shown in FIG. 4 enables energy measurement of neutral polarization with respect to mixing of the polarization states included in the main beam 401 in the energy measurement device 430. However, this configuration is not necessary for neutral polarization for the outgoing beam 404. The energy measurement of neutral polarization for the outgoing beam 404 should also take into account the change in polarization state generated by the main beam 401. Such a change may occur when the main beam 401 is delivered through the beam splitter 410 as the outgoing beam 404. In some embodiments, when optical means are added between the main beam pickoff assembly and the laser exit, additional changes may be made to the polarization state of the main beam 401 as the main beam 401 is transmitted as the outgoing beam 404. have. Moreover, if, for example, reflection at the rear surface is used to direct the outgoing beam 404 to the laser exit, a change in polarization state due to reflection at the additional surface needs to be considered. Since the sub-beam picked off from the main beam 401 is sent to the energy detector for the measurement of the laser energy, the polarization state of the beam at each energy measurement device preferably matches the polarization state of the beam at the laser exit. .

For example, an outgoing beam transmitted through the wedge-shaped beam splitter to the rear surface of the beam splitter arranged at the angle of the Brewster and to the front surface of the beam splitter disposed at 45 ° with respect to the incoming main beam 401 ( The polarization state of 404 is calculated as follows. The p-polarized element of the main beam 401 undergoes a 45 ° reflection at the anterior surface and 99.15% of the p-polarized light is transmitted through the anterior surface. The p-polarized light is transmitted entirely to the back side and arranged at the Brewster's angle. Thus, 99.15% of the p-polarized light included in the incoming main beam 404 belongs to the outgoing beam 404. On the other hand, 90.76% of the s-polarized light included in the main beam 401 is transmitted through the front surface, and 86.14% of the s-polarized light is transmitted to the rear surface oriented at the Brewster's angle. Thus, 78.18% of the s-polarized light included in the incoming main beam 404 belongs to the outgoing beam 404. Therefore, the polarization state of the outgoing beam 404 is different from the polarization of the incoming main beam 404 as a result of the reflection and transmission of the wedge shaped beam splitter.

In some embodiments, the pickoff assembly is used to produce a sub beam having a polarization state that matches the polarization state of the outgoing beam exiting the laser. This sub-beam can then be directed to an energy measuring device for the measurement of neutral polarization with respect to the outgoing beam. For example, referring to FIG. 6, the neutral polarized pickoff assembly 600 includes a beam splitter 610 and a beam splitter 620. The beam splitter 610 is a wedge shaped beam splitter with a front surface oriented at 45 ° to the incoming main beam 601 to generate the sub beam 602, similar to the embodiment shown in FIG. 4. However, unlike the embodiment shown in FIG. 4, instead of orienting the beam splitter 620 at 45 ° with respect to the subbeam 602, the beam splitter 620 is the polarization state of the transmitted main beam 604. Is adjusted to produce the sub-beam 603 in the energy metering device 630 that exactly matches. In some embodiments, the beam splitter 620 is oriented at an incidence angle of 66.05 ° relative to the sub beam 602 to produce a sub beam 603 that matches the polarization state of the main beam 604 transmitted at the laser exit. do.

Generally, the first of the two parallel planar beam splitters is arranged at an angle of 45 [deg.] With respect to the beam propagation direction, and the tilt angle of the second beam splitter is determined based on which reflection is used for each beam splitter. For example, considering the following two possible sets of configurations, these two produce sub-beams with the same s / p transmittance in the energy measurement device, as present in the transmitted main beam 604. (The listed numerical ratio is the transmission s / p for the first beam splitter):

Transmission main beam 604: 0.838

a) 45 ° anterior surface of the first beam splitter 10.83

45.98 ° anterior surface 0.0774 of the second beam splitter

Total of energy measurement 0.838

b) both surfaces of 45 ° of the first beam splitter 9.96

46.01 ° both surfaces 0.0841 of the second beam splitter

Total of energy measurement 0.838

In example a), the second surface of the first beam splitter is configured at the Brewster's angle, so that a ratio of 10.83 is obtained only in a single reflected beam. On the other hand, the second surface of the first beam splitter of example b) also contributes to the reflected beam because the degree of separation between the first surface and the second surface is small. That is, in example b), the ratio 9.96 is determined by (i) the reflection of the main beam at the first surface of the first splitter, (ii) the reflection at the second surface of the first splitter, and (iii) the first splitter's first splitter. 1 Obtained after passing through the surface. Similar considerations apply when the tilt angle of the first surface is different from 45 °, when the plates are not parallel planes, or when the tilt angles on both sides of the Brewster's angle are selected (eg, as shown in FIG. 5). Combination may be selected). In general, each of the first beam splitter and the second beam splitter is adjusted to provide a desired angle of incidence.

In addition to the configuration for the energy measurement of the neutral polarization for the incoming beam described in FIG. 4 and the energy measurement of the neutral polarization for the outgoing beam described in FIG. It is shown in. Referring to FIG. 7A, the assembly 700 includes a polarization rotator 730, in addition to the configuration shown in FIG. 6 described above. The polarization rotator 730 enables the measurement module to perform polarization measurement together with the energy measurement described above. The polarization rotator 730 may be inserted between the beam splitter 610 and the beam splitter 620 in the beam path of the sub beam 602 during polarization measurement. Both beam splitter 610 and beam splitter 620 are oriented in the same manner as shown in FIG. 6 when used for energy measurement of neutral polarization. Polarization rotator 730 alters the mixing of orthogonally polarized light of subbeam 602 to produce subbeam 603 with a mixture of different orthogonal polarizations. Thus, the mixing of the orthogonal polarization of the sub beam 603 directed to the energy meter 630 is no longer neutral polarization to the mixing of the orthogonal polarization of the main beam 601. Instead, the energy metering device 630 will record the signal following the mixing of the orthogonal polarization of the main beam 601 and, in turn, provide the polarization measurement of the main beam 601.

To illustrate the effect of the wave plate on the mixed light of orthogonal polarization measured in the energy metering device, consider a polarization rotator that rotates the polarization of the sub beam 602 by 90 °. Also consider the component of polarization (ie, p-polarization) parallel to the plane of incidence of beam splitter 610 directed from main beam 601 to sub beam 602. This p-polarized component is perpendicular to the plane of incidence of the beam splitter 610 after passing through the rotor 730 which rotates the p-polarized light by 90 °. That is, p-polarized light becomes s-polarized light. As described above, the plane of incidence of the beam splitter 620 is not parallel to the plane of incidence of the beam splitter 610. As a result, when incident on the beam splitter, the s-polarized light generated by the wave plate now becomes p-polarized with respect to the plane of incidence of the beam splitter 620. Therefore, the p-polarized component of the main beam 601 is reflected as the p-polarized light on both sides of the beam splitters 610 and 620 so that the sub-beam 603 is not neutral polarized for each beam splitter 610 and 620. ). In contrast, when the rotor 730 is removed from the path of the sub-beam 602, the p-polarized light (with respect to the beam splitter 610) becomes a s-polarized beam with respect to the plane of incidence of the beam splitter 620. Reflection at 620). In this case, the p-polarized element of the main beam 601 is subjected to reflections as p- and s-polarized light in the beam splitter 610 and the beam splitter 620, respectively. The low reflectance of the p-polarized light in the beam splitter 610 is compensated for by the high reflectivity of the same element of light beam now s-polarized with respect to the beam splitter 620. The sub beam 603 is thus neutral polarized light. The same analysis can be applied to the s-polarization element of the main beam 601 in a similar manner.

In some embodiments, polarizing rotator 703 is a birefringent wave plate having a fast axis oriented at 45 ° relative to the plane of oscillation of either s-polarized or p-polarized light with respect to beam splitter 610. (λ / 2-plate). Moreover, to avoid interference effects such as etalon in the wave plate, the polarization rotator 703 may be a wave plate having a somewhat wedge shape.

In certain embodiments, polarization rotator 703 may be formed from an optically active material, such as crystalline quartz. When light of linearly polarized light traverses an optically active crystal (e.g., a quartz crystal, etc.) along the optical axis, its polarization state remains the same but the orientation of the vibration plane of the electric field vector is at an angle depending on the distance traveled. Rotate Also referring to the axis of isotropy, the optical axis of the crystal is defined by the property that there is only one light propagation velocity related to the direction of the optical axis. In some embodiments, the thickness of the optically active crystal is selected to rotate the polarization of the sub beam 602 by an odd multiple of 90 °. For example, the optical activity of crystalline quartz at a wavelength of 193 nm is 324 ° / mm. Thus, the thickness of the polarization rotation made of crystalline quartz can be an odd multiple of 0.278 mm, and can be conveniently processed during manufacture. In addition, the polarization rotator based on the optical activity of the crystalline quartz is sufficiently insensitive to the thickness of the rotating plate, so that it can be somewhat wedge-shaped without significantly affecting the amount of polarization rotation of the transmitted beam.

In some embodiments, polarization rotator 730 may be manually inserted into the beam path of subbeam 602. Alternatively, polarization rotator 730 may be introduced into the beam path using an actuation mechanism (eg, an electromechanical or pneumatic actuator), as described below.

The sensitivity of the polarization measurement depends on the polarization imbalance of the sub-beam 603 when the polarization rotator 730 is inserted into the beam path of the sub-beam 602, and eventually, the beam splitter 610 and the beam splitter 620. Depends on the angle of incidence of and the rotation of the polarization transmitted by the polarization rotator 730.

8 is a measurement in which the mixing of polarization states of the main beam 601 has a polarization rotator 730 inserted in the beam path of the sub beam 602, and the measurement in which the polarization rotator 730 is removed from the sub beam 602. It shows how it can be determined based on. Referring to FIG. 8, lines 810 and 820 represent plots of relative signals in the energy measurement device 630 as a function of polarization ratio at the laser exit, with and without polarization rotation. . A polarization ratio of 1.00 indicates that the beam is completely p-polarized. Line 810 is a relative signal when the polarization rotator 730 shown in FIG. 7 is not inserted into the beam path of the subbeam 602, and line 820 is measured when the rotator 730 is inserted into the beam. Relative signal. When the polarization rotator 730 is inserted into the beam path of the sub-beam 602 and rotates the beam polarization by 90 °, the s-element of the beam (for the first splitter) is 127 times stronger than the p-element, resulting in energy measurement. Leads to imbalance. As a result, the s-element of the beam can be measured directly. As shown in FIG. 8, the overall transmittance is also high enough that small deviations from the complete p-polarization can be measured. The change in polarization rate from 100% to 97% (reduction in the amount of p-polarization) corresponds to an increase in signal from 9% to 26% at the detector when the polarization rotator 730 is inserted. Therefore, the polarization state of the main beam can be measured by the assembly 700.

In general, polarization measurements can be made using the assembly 700 using the following steps:

1. Measure the energy of the sub beam 603 directed to the energy measuring device 630 without the polarization rotator 730 in the beam path of the sub beam 602.

2. Insert the polarization rotator 730 into the beam path of the sub beam 602.

3. The energy of the sub beam 603 directed to the energy measuring device 630 with the polarization rotator 730 in the beam path of the sub beam 602 is measured.

4. Determine the energy ratio of the signal recorded in the energy meter 630 with and without polarization rotator 730.

5. Calculate the mix of polarization states of the main beams 601 based on the difference in the relative signals measured by the energy meter 630 when the polarization rotator 730 is inserted or removed from the beam path, and the measurement results again. The polarization ratio of the main beam 601 is determined by comparing with the calibration graph as shown in FIG. 8.

7B is a flow chart illustrating the method described above.

In the foregoing discussion, an embodiment for measuring either the neutral polarization of the main beam or the polarization state of the main beam has been described. However, in some embodiments, all of these beam characteristics are measured simultaneously. For example, referring to FIG. 9, the measurement system 900 includes a main beam splitter 910, a second beam splitter 920, an energy measurement device 930, a third beam splitter 940, and polarization measurement. Device 950. A portion of the metrology system 900 including the beam splitters 910, 920 is configured as shown in FIG. 6 for the energy measurement of neutral polarization in the energy metrology device 930 of the outgoing beam 904. do. The metrology system 900 directs the sub beam 905 using the beam splitter 940, which is transmitted from the beam splitter 920 for polarization metrology in the polarization metrology device 950. The beam splitter 940 is oriented so that its plane of incidence is parallel to the plane of incidence of the main beam splitter 910, but not parallel to the plane of incidence of the beam splitter 902.

As described in FIG. 7A, introducing the rotor 730 into the beam path at 602 hinders the initial neutral polarization measurement of the sub-beam 603. In some embodiments, the beam splitter 940 functions similarly to the polarization rotator 730 such that different blending of the polarization states measured in the polarization measurements compared to the mixing of the polarization states of the sub-beams 903 measured in the energy metering device. Can be used to generate the sub beam 906.

To illustrate how such measurements are made, consider a polarization element (p-polarized light) of light rays parallel to the plane of incidence of beam splitter 920. In the absence of a polarization rotator in the beam path of the sub-beam 902, this p-polarized element of light becomes s-polarized with respect to the plane of incidence of the beam splitter 910, reflecting off the main beam 901. The p-polarized component of the sub-beam 905 delivered through the beam splitter 920 is incident on the beam splitter 940 as s-polarized light with respect to the plane of incidence of the beam splitter 940. This s-polarization reflected by beam splitter 940 is also the s-polarization component of main beam 901. As described above, because the s-polarization component of the sub-beam 906 is the result of two reflections, that is, the reflection which is both s-polarization for each of the beam splitter 910 and the beam splitter 940. The light beam transmitted to the measuring device 950 is not neutral polarized light, and thus information on the polarization state of the main beam 901 may be obtained from the polarizing light measuring device 950. The same analysis can be applied to the p-polarized component of the main beam 901 in a similar manner.

In other words, as a result of the arrangement of the metrology system 900, the subbeam 906 is a mixture of orthogonal polarizations, similar to that obtained in the subbeam 903 only when a 90 ° rotor is inserted into the beam path of the subbeam 902. It includes. As a result, compared to the configuration shown in FIGS. 6 and 7 with an insertable polarization rotator 730, where the neutral polarization energy measurement and the polarization measurement must be made sequentially, the neutral polarization energy measurement and Both polarization measurements can be made simultaneously.

In general, two different sub-beams from two different beam splitters, coming from the main beam, can be used in the type of simultaneous measurement of the polarization state and the neutral polarization energy of the main beam.

In certain embodiments, in addition to performing simultaneous measurement of the neutral polarization energy and polarization state of the main beam using two measurement devices (e.g., energy measurement device 930 and polarization measurement device 940), two measurements Calibration between devices is possible. Referring to FIG. 1OA, the metrology system 1000 includes a polarization rotator 1060 that can be inserted further into the path of the subbeam 905, as compared to the metrology system 900. Other elements of metrology system 1000 are the same as shown in metrology system 900 of FIG. 9. The metrology system 1000 may also be used to calibrate the polarization metrology device 940 to the energy metrology device 930.

A method of using a polarization rotator that inserts a rotator in the sub-beam to hinder the initial neutral polarization measurement of the sub-beam has been described with reference to FIG. 7A. In the metrology system 1000, however, the polarization rotator 1060 performs the opposite function of rotating the polarization of the subbeam 905 to produce the subbeam 906 neutral polarization. Consider the case of polarization rotator 1060 which rotates the polarization of the s-polarization component (relative to beam splitter 920) of subbeam 905 by 90 °. This s-polarization component is due to the p-polarization component of the main beam 901 (as seen with respect to the plane of incidence at the beam splitter 910). Light rays of the s-polarization component of the sub-beam 905 relative to the beam splitter 920 will be transmitted through the polarization rotator 1060 and then become p-polarized light for the same plane of incidence of 920. This p-polarized light is reflected from the beam splitter 940 as s-polarized light with respect to the plane of incidence of the beam splitter 940. In other words, the sub beam 906 is the result of two reflections from the beam splitters 910 and 940. Considering the s-polarization component of the light rays contained in the sub-beam 906 for the beam splitter 940, these two reflections firstly p- polarization for the beam splitter 910 and s- for the beam splitter 940 Polarized light. By selecting two suitable angles of incidence in each of the beam splitter 910 and the beam splitter 940, the sub-beam 906 can be made with neutral polarization. As mentioned above, the two angles of incidence, one at the beam splitter 910 and one at the beam splitter 940 need not be identical, and the ratio of the reflectance of s-polarized light to p-polarized light (s If / p) is the same at two different angles, different angles can be selected, with the Brewster's angle back and forth.

As a result of polarization 1060 in the beam path of subbeam 905, both subbeam 903 and subbeam 905 are neutral polarization. The signals recorded in the energy measurement device 930 and the polarization measurement device 940 may then be calibrated with respect to each other, and thus polarization measurement calibration may be given. Such calibration is desirable in alternatives including calibrating the polarization metrology device 940 with an external polarization meter. Calibration may be necessary because of the degradation of photodiodes (also including UV-cured / expanded photodiodes) due to 193 nm laser light. In some embodiments, the photodiode is recalibrated after about 100 million laser scans. Alternatively, the power sensor 240 described with reference to FIG. 2 can be used to calibrate both the energy meter 930 and the polarization meter 940.

Performing polarization measurement and calibration using metrology system 1000 includes the following steps:

1. Insert the polarization rotator 1070 into the beam path of the sub beam 905.

2. The signal recorded in the energy measuring device 930 and the signal recorded in the polarization measuring device 940 are measured.

3. The energy ratio measured by the energy measuring device 930 and the polarization measuring device 940 is calculated.

4. Determine the calibration factor between the two measuring devices based on the percentage of energy measured in step 3.

5. Remove the polarization rotator 1070 from the beam path of the sub beam 905.

6. The signal recorded in the energy measuring device 930 and the signal recorded in the polarization measuring device 940 are measured.

7. Calculate the energy ratio or difference between the energy measuring device 930 and the polarization measuring device 940.

8. The mixing of the polarization states of the main beam 901 is calculated based on the difference in the relative signal measured by the polarization measuring device 940 when the polarization rotator 1060 is inserted or removed in the path of the beam, and the measurement result Again, the polarization ratio of the main beam 901 is determined by comparison with the calibration graph as shown in FIG. 8, and compared with the calibration coefficient determined in step 4.

10B shows the method described above in the form of a flow chart.

In some embodiments, subbeam 906 may be configured with neutral polarization in the absence of polarization rotator 1060 in the beam path of subbeam 905. In this embodiment, the calibration can be done directly without inserting the polarization rotator 1060 in the beam path. Instead, the polarization rotator 1060 is inserted into the beam path of the sub beam 905 when polarization measurements are made.

Performing polarization measurement and calibration using the system described above includes the following steps:

1. Remove the polarization rotator 1070 from the beam path of the sub beam 905.

2. The signal recorded in the energy measuring device 930 and the signal recorded in the polarization measuring device 940 are measured.

3. The energy ratio measured by the energy measuring device 930 and the polarization measuring device 940 is calculated.

4. Determine the calibration factor between the two measuring devices based on the percentage of energy measured in step 3.

5. Insert the polarization rotator 1070 into the beam path of the sub beam 905.

6. The signal recorded in the energy measuring device 930 and the signal recorded in the polarization measuring device 940 are measured.

7. Calculate the energy ratio or difference between the energy measuring device 930 and the polarization measuring device 940.

8. Calculate the blend of polarization states of the main beams 901 based on the difference in the relative signals measured by the polarization metrology device 940 when the polarization rotator 1060 is inserted or removed in the beam path, and again measure the measurement results. The polarization ratio of the main beam 901 and the calibration coefficient calculated in step 4 are determined by comparing with the calibration graph shown in FIG. 8.

1OC is a flow chart illustrating the method described above.

The foregoing embodiments have described various methods for obtaining neutral polarization energy measurements and polarization measurements, where the measurement module 120 is also used to measure other characteristics of the laser beam exiting the laser module 110. For example, the propagation direction of the laser beam is measured using the pointing measurement described in the following example. An exemplary embodiment of an apparatus for monitoring the propagation direction of a laser beam is shown in FIG. 11. Here, the pointing measurement apparatus 1000 includes a lens 1110, a photodiode 1120, a light conversion plate 1130, and a housing 1140. The apparatus 1000 monitors the propagation direction of the laser beam as follows. The lens 1110 focuses the laser beam 1101 (eg, a sub beam of the main beam of the laser system 100) on the light conversion plate 1130. The light conversion plate receives the laser light and converts the received radiation into radiation of another (eg, longer) wavelength. In some embodiments, light conversion plate 1130 converts incident incident UV (UV) light rays into longer wavelengths of visible light. For example, the visible light can have a wavelength between 500 nm and 600 nm. In some embodiments, the 193 nm radiation can be converted to visible light having a wavelength of about 550 nm. Light conversion can be performed, for example, by phosphorescence or fluorescence.

As an example, in response to the incident laser beam, the light conversion plate may fluoresce at the position where the fluorescent light is transmitted toward the photodiode 1120, which is located within the gap of the housing 1140. Fluorescence can then be detected by the photodiode 1120.

The photodiode 1120 may be a position sensitive detector (PSD) based on the horizontal resistivity of the photodiode (e.g., a commercially available PSD such as manufactured by Hamamatsu). The combination of lens 1110 and PSD allows for high speed reading of the signal, which automatically measures the center-of-mass of the beam spot incidence on the photodiode and the signal is independent of the actual beam divergence. Because. The PSD calculates the position of the beam spot based on the difference in photocurrent at the four electrodes along the edge. PSDs provide resolutions in the 1 μm range when low noise amplifier circuits are used. In some embodiments, lens 1110 may have a focal length of about 0.5 m for pointing metrology with a resolution of 20 μrad or less.

In some embodiments, the concentrated laser beam 1101 propagates in the purge volume, and the light conversion plate 1130 seals the purge volume relative to the housing 1140. In some embodiments, the photodiode is disposed outside of the purge volume and behind the photoconversion plate to minimize the risk of contamination and life issues.

The spatial distribution of the signal measured in the PSD can be calculated, for example, as described by the configuration shown in FIG. 12. This plot represents the calculated intensity spot on the PSD placed behind the light conversion plate with x and y axis scales in mm. Positioning the PSD surface 2 mm away from the light conversion plate (transducer) increases the size of the spot detected in the PSD to about 4 mm, providing a good average signal to the PSD surface. This enlarged spot can also be measured using a quadrant photodiode (QPD) in place of the PSD. The light conversion plate 1130 preferably has a plate thickness that is, for example, less than one quarter of the maximum dimension of the PSD, thereby maintaining a small sized fluorescent spot on the PSD.

In addition to the above embodiments, pointing metrology can be done by imaging the beam spot from the fluorescent plate to the diode, which can be coated with a fluorescent transducer or a UV-cured photodiode can be used without a light conversion plate. .

Scattered light in the PSD background degrades the detector's sensitivity, as the signal in the background does not change when the beam spot moves on the PSD. Possible sources of scattered light include scattered light from inside the metrology module and scattered light generated inside the fluorescent plate. In order to reduce background scattered light, in some embodiments, the maximum dimension of the fluorescent plate is greater than the sum of the maximum dimension of the PSD and twice the thickness of the fluorescent plate. By maintaining a small air gap between the light conversion plate 1130 and the PSD, the scattered light is trapped in the light conversion plate while undergoing total internal reflection of the light conversion plate, thereby preventing reaching the PSD. Increasing the diameter of the indium seal and the light conversion plate 1130 around the housing 1150 also helps to ensure that the scattered light does not reach the PSD. In addition, an adhesive layer or an absorbing layer may be applied to the light conversion plate 1130.

For various other measurements, the following describes determining other relevant characteristics of the laser beam exiting the laser module 110. For example, FIG. 13 shows a metrology assembly 1300 that includes a shutter, a metrology module 1310, and a core module 1320. The assembly 1300 is divided into at least two parts: The core module 1310 includes a main beam optic, a shutter mirror or shutter prism as shown in FIGS. 2 and 3, and the metrology module 1310 measures metrology optics. And a detector. In some embodiments, metrology module 1310 and core module 1320 are two separate purge volumes separated by windows that transmit beams from the first beam splitter in the main beam path to metrology module 1310. .

In further embodiments, several metrology devices are housed in the same metrology module. For example, referring to FIG. 14, the metrology module 1320 includes a CCD camera 1330, a metrology system for beam pointing, speckle contrast and 2D imaging of near and far field lasers. In some embodiments, the beam is attenuated to a certain level within core module 1320 such that a minimum amount of light enters metrology module 1320 to help reduce scattered light. Individual metrology modules can easily be replaced, repaired, and upgraded without having to remove the entire module, including the core optics and components, and thus do not affect the main beam. The individual metrology module may also be easy to transport and install if it is separated from the core module. Three metrology paths within the metrology module 1320 are created by reflections at the back and front of the wedge and the beam passing through the wedge. In addition, other partitioning / distribution schemes are possible.

Two-dimensional imaging of the laser beam provides a method of characterizing the beam quality of the laser beam exiting the laser module 110. For example, referring to FIG. 15, a two dimensional (2D) imaging assembly 1500 includes a convex lens 1510, a concave lens 1520, and a 2D camera 1530 used to image a laser beam. . 2D imaging of the near and far fields can be done with a very compact imaging assembly 1500. Near-field imaging is accomplished by transmission of metrology subbeams through convex and concave lenses for imaging (e.g., magnification 0.3), and far-field imaging is accomplished by transmission of metrology subbeams through convex lenses (e.g., By double reflection inside the concave lens (with a focal length of 400 mm). Imaging assembly 1500 is described in detail in DE 10 2006 018 804 A1, the content of which is incorporated herein throughout.

In general, the metrology detector may be disposed either within the purge volume and outside the purge volume of the metrology module. For example, referring to FIG. 16A, the detector assembly 1600 is housed in a purge volume. The detector assembly 1600 includes an internal CCD camera 1610 in the purged metrology volume 1650. The internal CCD camera 1610 may be, for example, a phosphor coated CCD camera.

Conversely, referring to FIG. 16B, the detector assembly 1605 includes a camera 1620 external to the purge volume 1660. Here, the detector assembly 1605 includes an objective lens 1630 and a fluorescent plate 1640 in addition to the camera 1620. Fluorescent plate 1640 may be made of doped glass or crystal to form a window that directs radiation out of the purge volume. The detector assembly 1605 may have the advantage that the electronics are not in the purge volume 1660.

In some embodiments, a single camera can be used to make one or more separate measurements of the laser beam. For example, FIG. 17 shows an image 1700 captured by one camera. Image 1700 includes a far field (diversity) image 1720 and a near field (profile) image 1710 of an excimer laser beam.

In some embodiments, speckle contrast of the laser beam can be measured. 18 shows a speckle metrology assembly 1800 that includes a spinning diffuser 1810, a focusing lens 1820, a convex mirror 1830, and a camera 1840. Spinning diffuser 1810 allows for measurements that are independent of the inhomogeneity of the camera. The focal length of the focusing lens 1820 should be long enough to resolve the speckle particles that accompany the pixels of the camera. In some embodiments, focusing lens 1820 has a focal length of about 1 meter for a camera with a pixel size of 6.4 μm. Telephoto arrangements include the configuration of convex lenses and convex mirrors. In some embodiments, telephoto devices may be used to help save space.

In some embodiments, additional features can be added to compensate for space limitations in some metrology modules. For example, FIG. 19 shows an additional folding mirror 1910 to reduce space to enable the speckle metrology assembly 1920 to fit within the metrology module.

The speckle metrology assembly 1800 may share a camera 1330 with 2D imaging for cost savings, as shown in FIG. 14. 20 shows a schematic layout of the profile measuring unit 2010, the divergence measuring unit 2020, and the speckle measuring unit 2030 on the camera 1330. The 2D imaging and speckle metrology beams may be placed next to each other on the camera 1330 (or fluorescent plate) using a split mirror, beam splitter or other optical element.

As described in the above embodiments, the shutter mirror 230, the shutter prism 330, the polarization rotator 730, the polarization rotator 1300, and other optical or ray detection apparatuses are temporarily used as the main beam or sub beam. Is inserted into the beam path. Such elements may be manually operated by electric DC motors, pneumatic cylinders or other mechanisms. If a motor or pneumatic cylinder is used to actuate the element, the motor or pneumatic cylinder may be located outside of the purge volume to avoid contamination of the purge volume. Mechanical feedthrough then connects an electrical or pneumatic actuator that drives an element inside the purge volume (eg, shutter mirror 230, polarization rotator 730, power sensor 140, etc.). Used to.

For example, referring to FIGS. 21 and 22, the positioning assembly 2100 may include a rotary shaft seal 2110, a lever arm 2120, a rotary actuator 2130, and an element 2140 to be driven (eg, a mirror). Optical elements, etc.). Rotary shaft seal 2110 is used to seal the mechanical feedthrough. Alternatively, a vacuum sealed feed through method such as a magnetic coupling device can be applied. Actuator 2130 may be driven manually or, for example, by a pneumatic or electric DC motor. Actuator 2130 may perform rotation at a defined angle, such as 45 ° or 90 °, in steps integrated into the actuator. Actuator 2130 rotates lever arm 2120 such that element 2140 is moved.

Linear actuators are used to drive optical or mechanical components, such as shutter mirrors or power meters. The linear actuator is pneumatically or magnetically driven. Referring to FIG. 23A, the actuator device 2300 houses a gas supply line 2130 (eg, nitrogen), a socket 2320, a bellow 2330, a pneumatic cylinder 2340, and an actuating member 2360. Mounting portion 2350 (for example, an optical member such as a mirror). The bellows 2310 seal the pneumatic cylinder 2340 which drives the operating member 2360 up and down. Bellow 2310 must be able to withstand many operating cycles. The bellows 2310 separates the purge volume in the space where the member 2140 is mounted from the actuator located outside the purge volume. Magnetic coupling devices are used for both rotational and linear operation.

In general, laser systems (eg, laser system 100) may be used in a variety of applications. In some embodiments, the laser system is used as the source portion of the lithographic exposure apparatus. Referring to FIG. 24, for example, laser system 100 is the source portion of lithographic apparatus 10. Projection exposure apparatus 10 includes an illumination system 12 for the generation of projection light 13, which illuminates the light source 14, the illumination optics indicated by reference numeral 16, and the aperture 18. It consists of In the illustrated embodiment, the projection light 13 has a wavelength λ of 193 nm. The projection exposure apparatus 10 also includes a projection lens 20 including a plurality of lenses, but only a portion thereof is shown by way of example in FIG. 24, and is denoted by reference numerals L1 to L5 because of clarity.

The projection lens 20 is used to image the mask 24 arranged in the object plane 22 of the projection lens 20 on a scale reduced on the photosensitive layer 26. The photosensitive layer 26 is composed of, for example, photoresist, is arranged in the image plane 28 of the projection lens 20, and applied to the carrier 30.

The carrier 30 is fixed to the bottom of the upper open container 32, such as a basin, which is movable in parallel with respect to the image plane 28 by a transverse movement device (not shown in detail). The container 32 is immersed in the immersion liquid 34 to the level at which the last lens L5 of the projection lens 20 is immersed on the side of the image immersed in the immersion liquid 34 while the projection exposure apparatus 10 is in operation. Is filled. Instead of the lens, the last optical element of the projection lens 20 on the image side may be, for example, a parallel plane terminal plate. The refractive index of the immersion liquid 34 is approximately equal to the refractive index of the photosensitive layer 26. In the case of projection light having a wavelength of 193 nm or 248 nm, high purity deionized water is available as the immersion liquid 34, for example.

The container 32 is a conditioning unit in which a member including a circulation pump and a filter for purifying the immersion liquid 34 is accommodated through an inlet pipe 36 and an outlet pipe 38. , 40). The adjusting unit 40, the inlet pipe 36, the outlet pipe 38, and the container 32 together form an immersion apparatus, indicated at 42, which allows the immersion liquid to be circulated while being clarified and maintaining a constant temperature. The absolute temperature of the immersion liquid 34 should be set as accurately as possible, because deviation from the reference temperature deteriorates the imaging by the projection lens 20 due to focus errors and defects in the image shell. Such deterioration of imaging eventually leads to a reduction in the size of the process window that can be used for exposure.

Other uses of laser system 100 include, for example, annealing flat panel members, surgical uses such as eye surgery, and dermatological uses. Other embodiments are described in the claims.

Claims (76)

As a laser system,
laser;
A housing comprising the laser and a first chamber disposed to receive laser radiation from the laser during operation of the laser system;
A first optical element that separates the first chamber from an adjacent chamber, is disposed in a path of a laser beam, and forms a window between the first chamber and the adjacent chamber;
A beam splitter disposed in a path of light upstream or downstream from the first optical element; And
A light detection device;
In operation, the beam splitter receives the laser beam, transmits a first portion of the laser beam as the main beam and directs the second portion of the laser beam as the first sub beam to the beam detection device. Laser system. The laser system of claim 1, wherein the light ray has a wavelength of less than 300 nm. The laser system of claim 2, wherein the light beam has a wavelength of 248 nm or 193 nm. The laser system of claim 1, wherein the laser is an excimer laser. The laser system of claim 1, wherein the laser consists of an argon fluoride lasing gas medium. The laser system of claim 1, wherein the beam splitter and the ray detection device are disposed in the first chamber. The laser system of claim 1, wherein a second portion of a laser beam that forms the first sub beam is reflected at the surface of the beam splitter. The laser system of claim 1, wherein the first optical element is a second beam splitter that directs a third portion of the laser beam as a second sub beam along a path different from the path of the main beam during operation. 9. The laser system of claim 8, further comprising a second light beam detection device different from the first light beam detection device, wherein the second light beam detection device is positioned to receive a second sub beam. The laser system of claim 1, wherein the optical element is a wedge-shaped element. The method of claim 1, wherein the optical element compensates for the deflection or offset of the main beam due to the beam splitter such that the path of the main beam is parallel to the path of light incident on the beam splitter after interacting with the optical element. Laser system. The laser system of claim 1, wherein the beam splitter directs the third portion of the light beam as a second sub beam in a direction different from the direction of the first sub beam. The method of claim 1, wherein the beam splitter comprises a first surface and a second surface that is not parallel to the first surface, wherein the first surface derives a first sub-beam from the light beam, and the second surface is A laser system for deriving a second sub-beam from said light beam. The laser system of claim 1, wherein the beam splitter is a wedge shaped device. The laser system of claim 1, wherein both the beam splitter and the optical element are wedge shaped elements. The laser system of claim 15, wherein all of the wedge-shaped elements have a first optical surface, and the first optical surface of the beam splitter is parallel to the first optical surface of the optical element. The laser system of claim 16, wherein a laser beam is incident on a first surface of the beam splitter, and a main beam of laser beam is emitted through a first optical surface of the optical element. 17. The laser system of claim 16, wherein both the beam splitter and the optical element have a second optical surface opposite and parallel to each other. The laser system of claim 15, wherein the wedge shaped elements all have the same wedge angle. The laser system of claim 15, wherein a portion of the wedge shaped element in the path of the laser beam consists of an uncoated surface. The laser system of claim 1, wherein either or both of the beam splitter and the first optical element comprise an uncoated optical surface. 21. The laser system of claim 20, wherein said first optical element is disposed such that a light beam is incident on Brewster's angle on at least one surface of said first optical element. The laser assembly of claim 1, wherein the chamber is sealed from the adjacent chamber. A chamber consisting of a first wall and a second wall opposite the first wall, the first wall comprising a first aperture and the second wall comprising a second aperture;
A first beam splitter disposed in the chamber in a path between the first and second apertures;
An optical element positioned in the second aperture; And
Including a ray detection device,
The beam splitter accepts light rays entering the chamber along a path through the first aperture, directs a portion of the light beam as a main beam to an additional optical element, and directs the second portion of the laser beam as the first sub beam. An assembly positioned to direct the light detection device. A device for measuring information about the polarization of a laser beam,
chamber;
Disposed in the chamber to receive a beam of light from the laser during operation to direct a portion of the beam along the first beam path as the main beam and to direct a second portion of the beam along the second beam path as the first sub-beam. A first beam splitter;
A ray detection device;
A second beam splitter arranged to receive the first sub beam, to derive a second sub beam from the first sub beam, and direct the second sub beam to the light detection apparatus; And
And an optical device disposed in a path of a first sub beam between the first beam splitter and a second beam splitter, the optical device configured to change a polarization state of the first sub beam. The method of claim 25, wherein the first beam splitter and the second beam splitter each have a reflective surface, and during operation, the reflective surface of the first beam splitter reflects a second portion of the light beam along a second beam path, and The reflecting surface of the second beam splitter reflects a portion of the light rays of the first sub-beam to form a second sub-beam, wherein the reflecting surfaces and the optical device have an orthogonal polarization in which the second sub-beam is substantially equal to the main beam. A device arranged to have a light with mixing. 27. The apparatus of claim 25, wherein the first beam splitter and the second beam splitter are arranged such that the second sub-beam has a radiation with orthogonal linear polarization mixing substantially the same as the main beam. 26. The apparatus of claim 25, wherein the first beam splitter and the second beam splitter are arranged such that the second sub beam has light rays with transmittance about two orthogonal linear polarization directions that are the same as the main beam. 27. The apparatus of claim 25, wherein the path to the ray detection device is devoid of diattenuation. 26. The method of claim 25, wherein each of the first beam splitter and the second beam splitter has a reflective surface, and during operation, the reflective surface of the first beam splitter reflects a second portion of the light beam along the second beam path. And the reflective surface of the second beam splitter reflects a portion of the light rays of the first sub beam to form a second sub beam, and the reflective surface is formed when there is no optical device in the path of the second sub beam. And the second sub-beam is arranged to have a mixed light beam of orthogonal polarization substantially the same as the main beam. The device of claim 25, wherein the optical device is a polarization rotator. 26. The apparatus of claim 25, wherein the polarization rotator is configured to rotate the polarization state of the first sub beam by 90 degrees. The device of claim 25, wherein the optical device comprises an optical element formed of a birefringent material. The apparatus of claim 33, wherein the optical apparatus is a retarder. 35. The apparatus of claim 34, wherein the retarder is a half-wave plate. The device of claim 25, wherein the optical device consists of an optical element formed of an optically-active material. 37. The apparatus of claim 36, wherein the optical device is a wedge shaped device. The device of claim 36, wherein the optically active material is crystalline quartz. 27. The apparatus of claim 25, wherein the ray detection device detects power of a second sub beam. 27. The apparatus of claim 25, wherein the ray detection device detects energy of a second sub beam. The apparatus of claim 25, further comprising a third beam splitter and a second light beam detection device, wherein the third beam splitter is located in a path of a first sub beam or in a path of a sub beam transmitted from a second beam splitter, And wherein during operation the third beam splitter is arranged to derive a third sub beam from a first sub beam or transmitted sub beam to direct a third sub beam to the second light beam detection device. 42. The apparatus of claim 41, wherein the third beam splitter is disposed in the path of the first sub beam between the first beam splitter and the second beam splitter. 43. The apparatus of claim 42, wherein the third beam splitter is disposed in the path of a first sub beam between the first beam splitter and the optics. 42. The apparatus of claim 41, wherein the first beam splitter, the second beam splitter, the third beam splitter, and the optical device comprise the second sub beam and the third sub beam defined by a path of respective sub beams. And arranged to have a polarization state substantially equal to said main beam with respect to a coordinate system. The optical beam of claim 41, wherein the first beam splitter, the second beam splitter, the third beam splitter, and the optical device are configured such that a polarization state of the third sub beam is defined by a path of respective sub beams. Arranged to rotate substantially 90 ° from the polarization state of the second sub-beam. 42. The method of claim 41, wherein the first beam splitter, the second beam splitter and the third beam splitter, wherein the second sub-beams and the third sub-beams, without the optical device in the path of the first sub-beams And an apparatus arranged to have substantially the same polarization state as said main beam. 42. The optical beam according to claim 41, wherein the first beam splitter, the second beam splitter, the third beam splitter, and the optical device have a polarization state of the third sub beam, and no optical device in a path of the first sub beam. And wherein the device is arranged to rotate substantially 90 ° from the polarization state of the second sub-beam. A device for measuring information about the polarization of a laser beam,
A first beam splitter;
A second beam splitter; And
Including a ray detection device,
During operation:
The first beam splitter receives a beam of light from a laser, directs a portion of the beam as a main beam along the first beam path, and directs a second portion of the beam as a first sub-beam along the second beam path;
The second beam splitter is arranged to receive the first sub beam, derive a second sub beam from the first sub beam, and direct the second sub beam to the ray detection apparatus; And
The first beam splitter and the second beam splitter are set such that the plane of incidence of the laser beam with respect to the first beam splitter is not parallel to the plane of incidence of the laser beam with respect to the second beam splitter. 49. The apparatus of claim 48, further comprising an optical device disposed in the path of the first sub beam between the first beam splitter and the second beam splitter, the optical device being configured to change the polarization state of the first sub beam. The apparatus of claim 48, further comprising a third beam splitter and a second light ray detection device,
The third beam splitter is located in the path of the transmitted beam of the second beam splitter,
In operation, the third beam splitter derives the third sub beam from the transmitted beam to the second light detection device, and
And the third beam splitter is configured such that the plane of incidence of the laser beam with respect to the third beam splitter is parallel to the plane of incidence of the laser beam with respect to the first beam splitter. 51. The apparatus of claim 50, wherein the third subbeam has light in a mixture of orthogonal polarization states that is substantially different from the second subbeam. 51. The apparatus of claim 50, further comprising an optical device configured to change the polarization state of the third sub-beam. 53. The apparatus of claim 52, wherein the third subbeam and the second subbeam are used to calibrate the first and second light detection devices. A method of monitoring information about the polarization state of a laser beam,
Separating the laser beam from the laser into a main beam and a sub beam;
Making a first measurement of the output or energy of the sub-beam;
Making a second measurement of the output or energy of the sub-beam, comprising: changing the polarization state of the sub-beam; And
Determining information about polarization of a laser beam based on the first measurement and the second measurement,
Determining the information includes calculating a ratio or difference between the output or energy of the first and second measurements. 55. The method of claim 54, wherein changing the polarization state of the sub-beams includes rotating the polarization state of the sub-beams by 90 degrees. A method of monitoring information about the polarization state of a laser beam,
Deriving a first sub beam and a second sub beam from a laser beam;
Making a first measurement of the output or energy of the first sub-beam using a first ray detection device;
Performing a second measurement on the output or energy of the second sub-beam using a second light detection device different from the first light detection device; And
Determining information about a polarization state of a laser beam based on the first measurement and the second measurement,
Determining the information about the polarization state includes calculating a ratio or difference between the output or energy of the first and second measurements. 59. The method of claim 56, wherein the first measurement and the second measurement are performed simultaneously. The method of claim 57, wherein the polarization state of the second sub-beam is rotated 90 ° from the polarization state of the first sub-beam. A method of monitoring information about the polarization state of a laser beam,
Deriving a first sub beam and a second sub beam from a laser beam;
Performing a first measurement on the output or energy of the first sub beam and the second sub beam using a first light beam detection device and a second light beam detection device, respectively;
Performing a second measurement on the output or energy of the first sub-beam and the second sub-beam by using a first light-detection device and a second light-detection device, respectively, to perform the first measurement or the second measurement Performing a second measurement, comprising rotating the polarization state of the first sub-beam;
Determining a calibration factor based on the first measurement, comprising: calculating a ratio or difference between a first measurement of energy of the first sub-beam and a first measurement of energy of the second sub-beam A calibration coefficient determination step; And
Determining information about a polarization state of a laser beam based on the second measurement and calibration coefficients,
Determining information about the polarization state includes calculating a ratio and a difference between the second measurement on the energy of the first subbeam and the second subbeam. 60. The method of claim 59, wherein simultaneously performing the first measurement using a first sub beam and a second sub beam. 60. The method of claim 59, wherein simultaneously performing the second measurement using a first sub beam and a second sub beam. 60. The method of claim 59, wherein a calibration factor is determined when the first and second sub beams have substantially the same polarization state as the main beam. The method of claim 59, wherein the polarization state of the second sub-beam is rotated 90 ° from the polarization state of the first sub-beam. A device for monitoring a change in the propagation direction of a laser beam,
A beam splitter arranged to derive the sub beam from the laser beam;
A sensor for monitoring a change in the position of the light beam on the sensor during operation;
An optical element disposed in a path of a sub beam between the beam splitter and the sensor of a light beam and focusing the sub beam on the sensor; And
A fluorescent plate disposed between the optical element and the sensor,
In operation, the fluorescent plate absorbs light rays of a sub beam of a first wavelength, emits light rays at a second wavelength different from the first wavelength, and the light rays of the second wavelength are detectable by the sensor. The apparatus of claim 64, wherein the optical element is a lens or a mirror. The apparatus of claim 64, wherein the sensor is a position sensitive diode. The apparatus of claim 64, wherein the sensor is a quadrant photodiode. The apparatus of claim 64, wherein the sensor comprises a detection surface having a maximum dimension, and wherein the fluorescent plate has a plate thickness less than the maximum dimension of the detection surface. The apparatus of claim 68, wherein the thickness of the plate is less than half the maximum dimension of the detection surface. The apparatus of claim 68, wherein the thickness of the plate is less than one quarter of the maximum dimension of the detection surface. 69. The apparatus of claim 68, wherein the fluorescent plate has a maximum dimension greater than the maximum dimension of the detection surface plus twice the thickness of the plate. 65. The apparatus of claim 64, further comprising a substrate supporting the fluorescent plate, wherein the substrate is positioned between the fluorescent plate and the sensor, wherein at least some of the light rays incident on the fluorescent plate during operation are directed to the substrate, and Wave guaded device to the edge of the substrate. laser; And
67. A system comprising the apparatus of claim 64, wherein during operation of the system the laser provides a laser beam such that the beam splitter derives the sub beam from the laser beam. The system of claim 73, wherein the laser is an excimer laser. The system of claim 73, wherein the laser beam has a wavelength of 248 nm or 193 nm. 74. The system of claim 73, further comprising an electronic processing device in communication with the sensor, wherein the electronic processing device is programmed to receive information from the sensor and to output information about a change in the direction of the laser beam.

Images